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IFR Alternate weather

Old 11-02-2008, 03:39 AM
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Default IFR Alternate weather

Reading through FAR 91.169,there is an area there that seems a little gray with regards to weather forecasts. Lets say that that there is a small airport located 20 miles from an airport that has TAF reporting, this small airport has a non precision approach only. Again, this small airport does not have weather reporting, can you use the TAF for the airport located 20 miles away in order to file the smaller airport as an alternate? I guess I kind of missed something along the way. I was always under the impression that the alternate of your choosing had to have forecast weather on the field.91.169 (c) references reports and forecasts or a combination of them. That is the part that plants the seed of doubt in my pea sized brain!
Thanks to all in advance.
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Old 11-02-2008, 04:21 AM
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You would have to check the approach charts, its not uncommon to see an airport that is not approved as an alternate "when local weather is not available" Seeing as a TAF covers 5 miles around the airport I would say you could not use that airport as an alternate based on the TAF but does an area forecast constitute local weather?
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Old 11-02-2008, 02:10 PM
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If the airport is not within the range of a TAF you have to use the FA (Area Forecast).
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Old 11-02-2008, 02:39 PM
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Tell me how does an area forecast tell you that an airport is IFR or VFR or not? Just because it say NRN Ca broken at 1800 doesn't mean that the airport is going to be the same as depicted. So if it don't have a TAF expect to descend from MEA in VFR and land in VFR. That would be my best guess.
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Old 11-02-2008, 05:48 PM
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I have to assume you meant no TAF on field, not no weather reporting station.

You use the FA as your forecast source; and what does the FA always say in bad wx? VIS 3-5SM. The FA covers your forecast requirement. Definitely check for alternate airport minimums before using such an airport as an alternate. Even if you can use it as an alternate w/o a TAF, you would check all area METARs and TAFs to get an idea what you're getting into. Part 91 makes a lot of flying legal that 121/135 restricts.

All the alternate airport filing requirement is for is to have some sort of plan before you blast off in IFR. You're not required to fly that approach or even land at your alternate. The METAR determines IFR/VFR (and for you Part 91 guys, you can even start the approach and determine for yourselves if you have the required flight visibility to land, but a favorable METAR can keep the administrator away).
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Old 11-02-2008, 07:17 PM
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Originally Posted by Riverside View Post
Tell me how does an area forecast tell you that an airport is IFR or VFR or not? Just because it say NRN Ca broken at 1800 doesn't mean that the airport is going to be the same as depicted. So if it don't have a TAF expect to descend from MEA in VFR and land in VFR. That would be my best guess.
An area forecast tells you the weather conditions of an area...if the area that your planned airport is in has cloud or visibility requirements that require an alternate, than you must file one accordingly. For this reason if bad weather plagues a state they break up the area forecasts more definitive than they do in good weather.

For example...

A good weather day may have:
TN...SKC OCNL SCT CI. OTLK...VFR.

Whereas a bad weather day may have:
W TN...SCT 050-070 VIS P6SM. OTLK...VFR.
NRN MID TN...BKN 005-014 VIS 1-3SM. OTLK...MVFR.
SRN MID TN...OVC 004-020 BR OCNL +RA VIS 1-3SM. OTLK...IFR.
E TN...BKN 025-050 VIS 3-5SM. AFTR 05Z ISOL -TSRA NRN HALF. OTLK...VFR.

TAFs are all well and good if you are flying to an airport with one, but if not then Alternate requirements and Alternate airport minimums (if allowed on the chart) must be taken from the FA.
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Old 11-02-2008, 07:31 PM
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That is not answering his question though. The FA will not tell you is you can shoot the approach or not. Basing you approach on the FA is not a good idea, when there is no TAF.
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Old 11-02-2008, 07:37 PM
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Originally Posted by Riverside View Post
That is not answering his question though. The FA will not tell you is you can shoot the approach or not. Basing you approach on the FA is not a good idea, when there is no TAF.
Forecasts are for planning purposes, and even TAFs are not spot on correct. You should base your approach on Enroute/Arrival weather you receive when you near your destination.

I was simply indicating that the FA is the legal way to go about alternate selection/application. Obviously for the most current weather you would want to obtain the ATIS, ASOS, or AWOS when you get close.

The exact answer to his question would be no, TAFs cannot legally be used for alternate selection or application unless the airport of intended use is within 5SM of the TAF airport. In which case the FA is uses in lieu of the TAF.
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Old 11-03-2008, 03:52 AM
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Thanks Woodfinx, that helps clear it up for me.
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